Efforts are being made in aircraft construction to employ components on an increasing scale that consist completely or at least partly of fiber-reinforced composite materials, e.g., carbon-fiber-reinforced plastics (CFRP), as structural or load-bearing components. For example, DE 10 2007 062 111 A1 describes a transverse-member structure consisting of carbon-fiber-reinforced plastic, which serves to support individual panels of an aircraft floor system for separating a passenger cabin from a cargo compartment arranged below the passenger cabin. Furthermore, it is known from DE 10 2007 062 111 A1 to employ components fabricated in a sandwich construction (i.e., with a core and outer (e.g., top and bottom) layers consisting of a fiber-reinforced plastic material applied to the core) as floor panels or ceiling panels in an aircraft.
For the purpose of producing components from fiber-reinforced composite materials, the reinforcing fibers are usually first introduced into a molding tool. Subsequently, the fibers are impregnated with the matrix material (e.g., polymer) which is typically provided in liquid form. Finally, curing of the matrix material is effected by appropriate control of temperature and/or pressure. Known methods for producing components from fiber-reinforced composite materials include injection methods, wherein the liquid matrix material is injected into a closed molding tool under elevated pressure of over 6 bar. Furthermore, infusion methods are known, wherein the reinforcing fibers are inserted into an open molding tool and are normally covered with a semipermeable membrane that is pervious to gases but impervious to the matrix material. The semipermeable membrane is covered by a gas-impervious film, so that an under-pressure can be applied between the semipermeable membrane and the gas-impervious film and, as a result, liquid matrix material can be drawn or sucked into the molding tool.
Irrespective of whether an injection method or an infusion method is employed for producing a component from a fiber-reinforced composite material, the control of the flow of matrix material into and through the molding tool is of crucial importance for the quality of the component. Thus, in the case of production of the component by an infusion method with an open molding tool, the flow of the matrix material is ordinarily monitored by means of a CCD camera. In the case of production of the component by an injection method with a closed molding tool, on the other hand, visual monitoring of the flow of matrix material is not possible, so sensors such as, for example ultrasonic sensors, line sensors that operate capacitively, temperature sensors and/or pressure sensors are employed. Generally, however, these sensor-based measuring systems do not provide continuous data on the actual advance of the front of matrix material in real time as the sensors only detect changes in the corresponding physical quantities at discrete locations.